Electrodes for proton exchange membrane fuel cells are typically made by mixing a slurry of carbon black with deposited platinum particles together with a liquid dispersion of ion conducting polymer solution. This slurry is then cast into a film and dried and the resulting film is a porous electrode that has a three-dimensional reaction zone with ionic conducting paths, electronic conducting paths and void spaces for reactant or byproduct transport. A continuing need for such structures is to balance the water content of the electrode and the underlying membrane with the open void space of the electrode for oxygen transport. It is known that the oxygen diffusion rate in water is roughly three to four orders of magnitude less than that in free air. Thus, if the catalyst sites are blocked with a film of water with any significant thickness, the reaction rate slows due to lack of oxygen transport. On the other hand, if not enough water is incorporated in the ionomer part of the electrode, then the ionic conductivity of the ionomer is drastically reduced, and the overall resistance of the cell increases. This balance is referred to in the literature as xe2x80x9cwater management.xe2x80x9d
The instant invention provides electrodes which aid in water management in fuel cells.
Specifically, the instant invention provides an electrode suitable for use in a fuel cell bearing a coating of at least one transport polymer. The invention further provides, in a fuel cell comprising at least one cathode and at least one anode and an ion exchange membrane separating the cathode and the anode, the improvement wherein at least one electrode bears a coating of at least one transport polymer.